1. Field of the Invention
The present invention relates to an electromagnetic valve for brake hydraulic pressure control valve and a brake control system having the same for vehicle, in particular, applicable to an ABS actuator for controlling vehicle wheel lock by increasing and decreasing hydraulic pressure.
2. Description of Related Art
The ABS actuator for an anti-skid control is provided with a hydraulic circuit composing fluid conduits and various control valves in which the control valves are operative for increasing/decreasing hydraulic pressure to be applied to wheel cylinders by controlling a communicating/interrupting state of each of the fluid conduits.
There is a pressure-increase control valve (normally open state valve), as one of the various control valves, for controlling the communicating/interrupting state of the fluid conduit connecting a master cylinder and each of the wheel cylinders.
The pressure-increase control valve is under a communicating state during a normal braking operation (not during the anti-skid control) and, thus, operative for allowing brake fluid to flow from a master cylinder side to a wheel cylinder side.
The pressure-increase control valve is turned to an interrupting state at a pressure-hold timing or a pressure-decrease timing during the anti-skid control in order to inhibit brake fluid to flow from the master cylinder side to the wheel cylinder side and switched to the communicating state at a pressure-increase timing during the anti-skid control in order to allow brake fluid to flow from the master cylinder side to the wheel cylinder side.
However, the conventional pressure-increase control valve has a problem that, when switched to the communicating state at a pressure-increase timing during the anti-skid control, large amount of brake fluid flows instantaneously because the diameter of the valve hole is defined to be large enough to allow brake fluid to flow during the normal braking operation. The instantaneous large amount brake fluid flow generates a hydraulic shock wave leading to a large pulsating pressure vibration that causes noises.